[RFI] TV Converter Boxes & RFI

dgsvetan at rockwellcollins.com dgsvetan at rockwellcollins.com
Tue Apr 22 18:59:49 EDT 2008


I understand the issue raised by Dick (his comments below), but those 
comments apply to the radiated spectrum from the TV transmitters 
themselves and the effects upon the local areas in which those 
transmitters operate.  The issue you raise has to do with the noise in the 
local spectrum at and around your QTH as a result of a cable-based system. 
 That issue is more controlled by the following factors:

- Quality of the cable and the connectors used (ie, RF "leakage")

- Quality and design of the interface boxes (how much do the interface 
boxes for Bright House leak, in what part of the spectrum do they leak, 
and are they susceptible to nearby transmitters?)

- Quality and design of the box that goes inside the house at your TV 
(same issues as above)

Depending upon your main frequency bands of concern (HF, 6m, 2m, 
whatever), I would take a portable or mobile receiver that covers the 
bands in which you are interested and visit a neighborhood in which this 
system is active.  Listen for increases in the noise spectrum as heard on 
the receiver or for interference to stations that you have tuned in.  Of 
course, that is not as definitive as evlauating it in your house, but it 
might give you enough input to make a tentative decision.  If you decide 
to get the service, be sure that you can get a refund if it interferes or 
if the system gets clobbered by your transmitters.

As you walk or cruise around, try to place your portable or mobile radio 
at a distance similar to that which would apply at your QTH.  Remember, 
it's not where the radio will be, it's where your antennas wiill be that 

73, Dale

kd4e <doc at kd4e.com> 
Sent by: rfi-bounces at contesting.com
04/19/2008 04:35 PM
Please respond to
doc at kd4e.com

RFI List <rfi at contesting.com>, "tvi-rfi-emi at mailman.qth.net" 
<tvi-rfi-emi at mailman.qth.net>
w7tio at juno.com
[RFI] TV Converter Boxes & RFI

Since they just ran a Bright House cable next door in our
*very* rural neighbohood (10 acre lots) to a pole that is
about 120 feet from the house should we anticipate a rise
in RFI?

If I we to allow them to run the cable to our house would
that increase RFI?

> First a comment.. This subject DOES impact ham radio, for in a larger
> city with multiple Digital TV stations, which are normally "megawatt"
> stations, the noise floor for VHF repeater inputs rises accordingly,
> for digital pulses are full of spectrum noise!
> In Portland, Oregon with channels 2, 6, 8, 10, and 12, and not all 
> converted yet, it rose 20db! This translates out to a factor of some 
> 120 times the origional noise!!
> Dick, CET (I'm licensed TV tech!!)


Thanks! & 73, doc, KD4E
Free OS : http://www.ChurchPup.com
Based on: http://www.PuppyLinux.com
Personal: http://bibleseven.com/kd4e.html
             | | & | |
        /\      {|
       /  \     {|
      /    \    {|
     /   @  \   {|
     |   |~_|~~~~|
     |   -| |    |
============\ # KD4E
RFI mailing list
RFI at contesting.com

More information about the RFI mailing list